氧化鋁矽奈米管在液體中動態行為之數值研究

氧化鋁矽奈米管具有超過鋼鐵的機械強度、優良的質量傳送性質與催化特性，為相當被看好的材料。因為水熱法的製備過程，合成氧化鋁矽奈米管會直接被分散在溶液相形成奈米流體。然而奈米流體中的奈米粒子容易因為聚結而使尺寸上升到微米的尺寸，失去奈米等級的特性；並且尺寸的變異可能導致反應性、毒性的改變，進而造成對環境的影響。因此，本論文旨在探討氧化鋁矽奈米管在溶液中的動態行為與添加劑可能造成的影響。本文以能節省計算資源同時具備保留溶液特性的粗粒化分子動力學進行以下三項研究：(1)外加強作用力之球狀粒子對溶液動態行為之影響，(2)外加強作用力之鏈狀粒子對溶液動態行為之影響，(3)外加界面活性劑(具有雙性質之鏈狀粒子)對溶液動態行為之影響。就第(1)項，我們發現當外加粒子的作用力高於背景溶液五個數量級時，外加粒子會群聚在一起，並且，這個數量級差距與過去準確描述氧化鋁矽奈米管的CLAYFF力場中強作用力與弱作用力的量級差距相同，可能為添加劑的影響足以跨越布朗運動造成沉澱的關鍵尺度。第(2)項則是延續第(1)項具有關鍵影響的五個數量級，改變外加粒子的型態，在這個部份我們發覺外加粒子的長度越長，奈米管的排列越接近平行的狀態，也就是外加粒子的形式與奈米管的排列有高度的相關性。第(3)項考慮界面活性劑這種雙性質粒子在不同作用力下可能造成的影響，與第(1)項類似的是五個數量級仍為具有影響差異的關鍵點，在超越這個數量級時，界面活性劑可以形成微胞增加有效半徑，幫助奈米管分散於溶液之中。從本文數值計算結果，得知在氧化鋁矽奈米管的溶液系統中，添加劑的作用力與型態皆為影響粒子動態行為的重要因素。以上這些分析測試除了讓我們更了解氧化鋁矽奈米管動態行為背後的作動機制外，希望本論文對日後欲投入相關研究的學者或應用方面上也能有所幫助。

關鍵字

氧化鋁矽奈米管；動態行為；粗粒化計算；分子動力學；添加劑

並列摘要

Aluminosilicate nanotube is a promising material because it possesses mechanical strength that exceeds that of steel, as well as applications in catalysis and molecular transport. Due to the preparation of being synthesized hydrothermally, nanotubes will suspend in the solution simultaneously. However, the nanotubes could collide one another and form agglomerates with time, forming micrometer-size structures and losing some unique characteristics associated with nano objects. At the same time, reactivity and toxicity could be varied as the nanotubes agglomerate. Therefore, the goal of this thesis is to study the dynamic behavior of aluminosilicate nanotubes in liquid. We will use coarse-grained molecular dynamics in this study, and focus on: (1) the effect of spherical additives, (2) the influence of chain additives with different lengths, and (3) the influence of surfactant. For item (1), we found that when the interaction between nanotubes and additives was approximately five orders of magnitude stronger than that between nanotubes and solvent, nanotubes could form agglomerates. Such an order of magnitude for force interaction is the same as the gap between stronger interaction and weaker interaction in the CLAYFF force field, which describes the aluminosilicate nanotube well. Such a force scale could possibly the key scale to overcome the agglomeration associated with the Brownian motion. Continued with the key scale, we studied the chain additives with different lengths in item (2). The result showed the longer the length of additives was, the more parallel pattern for nanotubes was observed, i.e., the arrangement was correlated highly with the length of additives. For the simulations by adding surfactants in item (3), as in item (1), five orders of magnitude was also the key scale for force interactions to forming micelles, aiding the suspension of nanotubes in solution. It was found that the types of additives are crucial for the dynamic behavior of aluminosilicate nanotubes in liquid. It is hoped that the present study can not only provide us a better understand of the wherefore of dynamic behavior of aluminosilicate nanotubes in liquid, but also is helpful for further research and application.

並列關鍵字

Aluminosilicate nanotubes ； dynamic behavior ； coarse-grained calculation ； molecular dynamics ； addictives

參考文獻

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國際替代計量

氧化鋁矽奈米管在液體中動態行為之數值研究

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